Essay
P5
- Institution
- PEARSON (PEARSON)
This document was written in 2017 and was marked to the standard of merit.
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Open Loop ControlOpen loop systems require things called open loop controllers which help the system
achieve a specific task, most of the time the open loop system will look at the input for it to
know what it needs to achieve. However, sometimes the output is not important for that
specific system. An example of a open loop control system is switching on a light bulb,
tumble drier, remote controls, washing machines etc…
An in depth example of an open loop control system would be a microwave or washing
machine, the machine is told a time to perform a certain task at a certain temperature/speed.
Say you set your microwave to two minutes, the microwave will heat your food for exactly
two minutes because you told it to. It doesn’t matter if the food is burnt, undercooked or
perfect, it will do what it’s told but it won’t be able to know if it’s actually cooking what you’re
putting in.
The advantages of open loop control systems are:
● Easy to maintain
● Easy construction
● Simple Design
● Low Cost
There are no real disadvantages to an Open loop system it just does not have some of the
features a closed loop has, such as, automatic readjustment.
Closed Loop Control
Closed loop systems have to monitor the input and output to make sure that specific tasks
are met, if these tasks are not met then often or not it will automatically correct itself. For
example, when a central heating senses that the temperature it’s trying to put out isn’t met it
will either turn up or down until the temperature is correct. This is done by the use of a
sensor which monitors the output and will adjust itself to reduce the amount of errors and
achieve the desired temperature (outcome). There are also many other devices that use
closed loop control systems, such as water level control, air conditioner, car cooling system
etc…
The advantages of closed loop control systems are:
● More accurate
● Automatically Adjusts
● Automatic
● Higher Bandwidth
The disadvantages of closed loop control systems are:
● More expensive than Open Loop
● Requires more maintenance
● Maintenance costs are often more
● Less stability
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